ABSTRACT Cannabis is the most commonly used illicit drug in the United States. Although cannabis use is widespread and basic science research on cannabinoids is well-developed, advancements in medication development for cannabis use disorder (CUD) have been limited. Varenicline, a selective nicotinic nACH receptor partial agonist of the ?4?2 subtype and a full agonist of the ?7 subtype, is arguably the most effective pharmacotherapy for promoting tobacco abstinence, and has also shown promise for the treatment of alcohol use disorder. Varenicline may improve cannabis use outcomes through multiple mechanisms, including interaction with the mesolimbic dopamine system, enhancement of cognitive functioning, and restoration of inhibitory control. To date, however, varenicline has not been evaluated in individuals specifically seeking treatment for CUD. In this UG3/UH3 application, we propose to rapidly yet thoroughly assess the utility of varenicline for CUD to potentially advance varenicline through the FDA's drug development approval pipeline. In the UG3 component, we will conduct a six-week, placebo-controlled proof-of-concept clinical trial of varenicline for CUD, paired with pre- and post- evaluations of cognitive functioning and neural circuitry involved in cannabis cue reactivity and inhibitory control to elucidate the pharmacodynamics of varenicline as a treatment for CUD. If milestones of the UG3 component are met, the UH3 project will be an adequately powered 12-week clinical trial with follow-up to fully assess the efficacy of varenicline in this population.